Moving into less known territory here but I think because the RB20 requires less air. I'm guessing it would have to have less torque too but it's probably in a lighter car with who knows what other mods for an 11 second pass.
People here have tried it on an RB25 and despite others telling them that they can get 250 they never can. There is all sorts of talk about boost controllers and waste gates actuators but in the end it doesn't seem to be able to push enough air into the RB25.
I'm sure a stock turbo can push 200 rwkw at 1 bar, in fact, probably at a little under one bar.